1. Field of the Invention
This invention relates to a method for transferring a nano material from a substrate to another substrate, more particularly to a method involving heating a first substrate on which a nano material is formed so that heat is conducted substantially from the first substrate through the nano material to a second substrate to which the nano material is to be transferred.
2. Description of the Related Art
As dimensions of electronic devices continue to scale down, nano materials, such as nanowires, nanorods or carbon nanotubes (CNTs), have been developed for application to nano-devices. In addition, nanowires, nanorods and carbon nanotubes (CNTs) exhibit excellent field emission (FE) property and thus are ideal materials for making devices, such as field emission displays (FEDs).
Since the carbon nanotubes (CNTs) are flexible and semi-conductive, they can be used to manufacture flexible electronic devices, such as flexible field emission displays. Conventionally, manufacture of the flexible electronic devices involves transfer of the carbon nanotubes (CNTs) from a hard substrate (e.g., a Si substrate), that can endure a high temperature for deposition of the carbon nanotubes (CNTs) thereon, to a flexible substrate (e.g., a polycarbonate (PC) substrate).
FIGS. 1A to 1C illustrate consecutive steps of a conventional method for transferring a CNT array pattern 111 from a Si substrate 11 to a flexible substrate 12 so as to form a nano-material integrated substrate (see Nanotechnology, 19 (2008) 465303 (6 pp) disclosed by the inventor of the present invention). The conventional method includes the steps of: (a) forming the CNT array pattern 111 on the Si substrate 11 (see FIG. 1A); (b) placing the flexible substrate 12 made from polycarbonate on a top end 112 of the CNT array pattern 111 and then heating the assembly of the Si substrate 11, the flexible substrate 12 and the CNT array pattern 111 in a microwave reaction chamber (not shown), the heating being conducted under an output power of 400 W of the microwave (MW) reaction chamber for 30 seconds to 60 seconds so as to soften a surface 121 of the flexible substrate 12 and to allow the top end 112 of the CNT array pattern 111 to extend into the softened surface 121 of the flexible substrate 12 (see FIG. 1B); (c) cooling the assembly so as to permit hardening of the softened surface 121 of the flexible substrate 12 and solid bonding of the CNT array pattern 111 to the flexible substrate 12; and (d) removing the Si substrate 11 from the CNT array pattern 111 so as to form the nano-material integrated substrate (see FIG. 1C). Although the aforesaid method can be used to transfer the CNT array pattern 111, it tends to suffer from the problem of incomplete transfer, i.e., a portion of the CNT array pattern 111 remains on the Si substrate 11 after removal of the Si substrate 11 from the CNT array pattern 111. FIG. 2 shows an experimental result of transferring the CNT array pattern 111 from the Si substrate 11 to the flexible substrate 12 using the microwave reaction chamber as a heating means. The result shows that only a portion of the CNT array pattern 111 is successfully transferred from the Si substrate 11 to the flexible substrate 12 after removal of the Si substrate 11. As a consequence, the nano-material integrated substrate thus formed has detects and is not suitable for manufacturing the aforesaid electronic devices.
Therefore, there is a need in the art to provide a method that can substantially transfer the entire nano material from a first substrate to a second substrate.